Cadmium plating composition



' solution and control the character of eposit.'.

Patented I Jan. 3, 1933 UNITED STATES.

PATENT OFFIC GEORGE B. no eanoom, or mew BRITAIN, connno'riou'a'jann MVYRON' 1a,,nroo1n, or marawm, new messy, assrenons r mmsou-vanfwmxns-munnme com PANY, or marawan, New JERSEY, a con ronarro'n or NEW JERSEY,

camnom rm'rme COMPOSITION ll'o Drawing.

The present application is a continuation in part of our rlor applicationISerial No. 554,150, filed J-u y 30, 1931.'

This invention relates, to an improved com- 5 position of electrolyte for use inthe electrodeposition of cadmium.

The electrodeposition of cadmium hasbeen successfully employed more particularly wit'h alkaline or cyanide solutions. The character ofdeposit when employing simple solutions of for example cadmium oxide and sodium cyanide in water-is not satisfactory, both on account of poor throwing power and on account of the granular,fdull oruneven tory for commercial practicetwi.

tion is to provide animproved'composition of electrolyte; eitherin'the form of a mixture or compositionof dry; chemicals ready to be dissolved, or in the form-ofian already prepared solution, .to enable the electroplaterto produce cadmiumplatingfof a fine,- uniform,-

dense structure an oia good bright appearance whichwill greatly enhance the .value of 4 the plating both from'aprotective standpoint and from the standpoint "of attractiveness. On account of the increased throwing power whichresultsffrom the composition employed in accordance with our invention, the electrolyte is particularly. advantageous in the plating ofirregular-shaped articles or sur iaces.- -v v 35, In-anattem t to derive a more compredissolved or suspended in the electro lating' Such investigation has led us to recognize the peculiar effect of certain types of organic identifie compounds, and particularly those compounds which have a fiveor six-membered oxygen-containing heterocy'clic Comstructure of the deposit, which is unsatisfie- .;lpplication filed July 21, 1932. Serial lid-623,818.

pounds of this class may be relatively simple or comparatively complex-in their molecular structure, but our investigations indicate that the presence of. the oxygen-containing heterocyclic ring in such compounds has .a ver important efl'ect on the character ofthe ca mium deposit when such compounds are to be employed in alkaline plating solutions such as for-example those which contain sodium cyanide and a cadmium salt in the 'presence of another alkali compound, such as vcaustic soda or sodium carbonate. I I

1 As examples of compounds having heterocyclic oxygen-containin rings, which we have. found to be useful %or our present purposes, we may mention furfural, furfuryl, a cohol, tetrahydro furfuryhiuroic acid, (1

haemateinJ The-first four of these compounds -contain fiVe-membered oxyheterocyclic rings and the fifth com ound contains a six-membered oxyheterocyc icring. I

In making up the composition for use as an electrolyte, considerable latitude is permissib1e, but typical examples, will be iven for the purpose of. clearlyiillustrating t I e invention. In" these examples it may be; assumed thatfthe major. portion of the composition is made up. "of 85% sodiumv cyanide and 15% cadmium. oxide. f Of this mixture,-plus the stated amountof one of the additionagents to be" added in'accordance with our invention,'an' aqueous solution can be made in proportionssof 120 gms, per L. 4 Sufficient of the j addition agent is added either to the mixture hensiveiview o the principle 'to be employed; for obtaining the new character. of cadmium deposit, wehave madecxtensive investiga- I tion of chemical compounds. which couldbe to be. dissolved in water; or to thesolution ralready formedptogrepresent the following Tetrahyd'ro furfuryl (11.0), (18.0);or

(22.0) c. c. per'L. p Furoic'acid L 2.0 to 14.0 'gms. per L. -.Haematein-; r e0.8 to--12.0 gms. per L.

The addition of furoic acid to. the usual 9'5 .cyanideplating solution will produce sodium furoate. This salt may, if desired, be added directly in proper amounts, such as ,for ex- ..ample, to represent a. chemical equivalent of p the furoic acid mentioned inthe foregoing yl' alcohol; 9.0 to 12.0 'c. c. per L. t v

and are included within the scope of our present invention. Furthermore, mixtures of two or more addition agents may be em= ployed. For example, a mixture of sodium furoate andfurfural-caustic alkali resin in the proportions of-80% furoate and 20% resin is particularly satisfactory. The mixture may be produced in suitable condition for our purpose, by adding 50 gms. caustic soda in aqueous solution to 122 gins. furfural and 100 c. 0. water at the boiling temperature, in-a suitable'v'essel fitted with a reflux condenser. After ten minutes refluxing, the resinate solution thus produced may be mixed with an aqueous solution c? 600 gms. sodium furoate and the mixture evaporated to dryness under vacuum of, say, 22 inches. The product in the form of a dry powder containingsodium furoate and the alkali resin-is then ready for use in making up the cadmium plating composition. This addition agent may be used in cadmium plating solutions in the proportions of,for example,2 to 15 gms. per liter of solution. Somewhat smaller. proportions will give a noticeable brightening effect, and larger proport ons have been used in some cases. In general, it is believed that the proportions of brightener can be increased as the metal concentration is increased. In solutions having a metal concentration of about 15-to 20 gms. per liter, a proportion of 7 or 8' gmslof this brightenerper liter of solution, appears to be aboutthe optimum.

maaaea of these particular materials. Some of these compounds, such as for example sodium furoate and furfural caustic alkali resin, (and to a somewhat lesser degree haematein,) are superior to-the others in that they produce a more marked brightening effect upon the cadmium, but the brightening efl'ect is produced also by the others, only not to such a marked extent. The presence of the furan ring appears to be important in the effect.

We claim I 1. A cyanide cadmium plating composition comprising an oxyheterocyclic ring compound.

2. A cyanide cadmium plating composition comprising an oxyheterocyclic ring compound in which the ring is more than fourmembered and less than seven-membered.

3. A cyanide cadmium plating composition- 1 comprising an oxyheterocychc compound containing the furan ring.

4. A cyanide cadmium plating composition comprising an alkali metal furoate.

5. A cyanide cadmium plating composition comprising haematein.

6. A cyanide cadmium plating composition comprising furfural.

7 A cyanide cadmium plating composition comprising. a caustic alkali furfural resin.

8. A cyanide cadmium plating composition comprising an alkali metal furoate and a'caustic alkalifurfural resin.

9. A cyanidecadmium plating composition comprising. an alkali metal furoate and a caustic alkali furfural resin in the respective proportions:of'80% furoate and'20% resin.

10. A cyanide cadmium plating solution comprising as a brightener in the ratio of from two or fifteen grams of 80% alkali metal furoate'and 20% caustic alkali furfural resin per liter solution of fifteen to twenty grams per liter metal concentration.

' GEORGE B. HOGABOOM.

MYRON B. DIGGIN.

The solutions made up in the manner set forth by way of illustration, may be employed at room temperature at a current density of 10 to 15 amperes per square foot of cathode area. This current densit =may be varied considerably without loss 0 the beneficial results, and particularly where agitation of the solution is maintained during operation." In

, the case of haematein, for example, we have successfully employed 30 amperes per square foot of cathode surface by maintaining agitation during the platingo eration.

In accordance with we I understood rinciples, cadmium anodes or insoluble ano es or combinations of the two may be employed.

While the above compounds have been mentioned as examples of addition agents or brighteners containing fiveand six-membered oxyheterocyclic rings, we wish to be distinctly understood asnot limited to the use 

